Many jobs require the use of hand held paint spray guns. These include certain jobs in manufacturing and jobs in automotive refinishing shops, for example. When an operator is required to frequently use a spray gun over a long period of time, the operator may develop fatigue in the hand and wrist. Fatigue can be aggravated by repetitive motions, such as by frequently squeezing the spray gun trigger with the same finger motion, by unbalanced forces on the hand and wrist, by the weight of the gun and by the force required to operate the gun trigger.
A typical prior art hand held paint spray gun includes a gun body having a nozzle assembly mounted on one end and having a handle depending from adjacent an opposite end. A trigger is attached to the gun body to pivot towards and away from the handle. When an operator holds the gun by the handle and squeezes the trigger, an air valve is opened and then a valve needle is moved to open a fluid valve. The air valve supplies any air required for atomization and for shaping the spray pattern. If the trigger is only partially squeezed, the fluid valve may be only partially opened to permit the operator to apply a lighter coating, for example, for feathering when touching up a coating. The spray gun also includes an adjustable stop which limits either trigger travel or the valve needle travel to adjust the maximum paint flow from the gun when the trigger is fully squeezed. In the prior art hand held spray gun, the trigger has a relatively long travel. Consequently, the operators fingers must move the trigger over a relatively large arc when squeezing or releasing the trigger. Also, a relatively high force has been required to overcome friction when squeezing the trigger and to assure that the gun turns off when the trigger is released.